Cbw protective clothing

ABSTRACT

A composite material suitable for use as CBW protective clothing comprises, in combination: 
     an outer layer (1) of an abrasion-resistant, water-repellent material; 
     an intermediate layer (2) comprising activated charcoal cloth treated to provide liquid-repellency; and 
     an inner layer (3) of an abrasion-resistant material laminated to the intermediate layer. 
     This composite is light, breathable and has low thermal insulation properties, but provides good chemical protection.

FIELD OF THE INVENTION

This invention relates to protective materials, and especially toclothing intended to be worn as complete protection from a contaminatedenvironment.

BACKGROUND OF THE INVENTION

Protective suits may be required to protect the wearer against a varietyof chemical and biological agents. For example, protection is requiredagainst droplets of certain agents which may affect the skin, andagainst vapours of the same or other agents which are a threat to therespiratory system. Toxic biological agents may be in the form of sporesand are therefore a particulate threat, which can only cause casualtiesif inhaled or if allowed to penetrate into the body through an openwound. There are also biological agents which present a hazard if theyare delivered in the form of a liquid agent which can penetrate theskin.

Heat stress is universally recognised as being the greatest limitingfactor for the achievement of a suitable protective clothing system.Attaining total chemical protection in a clothing system is notdifficult. Impermeable materials such as butyl rubber are available togive such protection. However, any non-breathable clothing system willprove unwearable under most conditions in a matter of minutes. It is nogood providing total protection if it results in the wearer losing hiseffectiveness.

It has therefore been attempted to develop an anti-gas fabric which notonly protects but which allows air to penetrate and water vapour fromthe body to permeate out. Filtration of the chemical liquids and vapoursis therefore required, and activated carbon is a well-known andeffective adsorbent.

All clothing systems need to be flexible, and therefore earlydevelopment revolved around impregnating a suitable textile carrier withactivated carbon adhered to it, i.e. creating a synthetic activatedcarbon material. Many approaches have been developed: impregnatedpolyurethane foam, non-wovens with bonded charcoal, carbon-filledspheres bonded to a carrier material. All of these approaches have twomajor limitations, i.e.

a) inability to provide sufficient carbon on the surface of the carryingmaterial without blocking off its breathability; and

b) degradation of the charcoal due to aging of the bonding process.

Other common limitations present in some or all of these systems are:shedding of charcoal through abrasion, lack of launderability and, mostimportant of all, lack of breathability and high thermal insulationproperties.

There are different aims reflected in known protective clothing systems.Each system reflects both the technology available and a particularprotection philosophy.

For example, if it is decided that very high protection levels arenecessary, an anti-gas system may be based on a polyurethane foam loadedwith activated carbon powder. The disadvantages encountered by such asystem are as follows: the high insulation properties of thepolyurethane foam make the physiological load on the wearer undesirablyhigh, and the high carbon loading necessitated by the high protectionfactor increases the weight of the garment and reduces itsbreathability, and therefore also increases the physiological load.

An alternative aim is to balance adequate protection and a reasonablephysiological burden. To this end, a known anti-gas fabric is afluorochemical-treated non-woven which has been coated with fine activecarbon particles fixed with a polymeric binder. However, although thephysiological burden on the wearer is reduced in this case, theprotection offered by this system is not sufficient to allow it to beworn as an integral uniform, only as a protective overgarment.

PRIOR ART

GB-A-2096536 describes a composite protective material comprising atwo-layer cloth structure, one layer being oil/water-repellent and theother being an adsorptive charcoal. For use as a protective material, 4layers are required. The innermost layer is moisture-absorbent, but willnot prevent sweat poisoning.

EP-A-0150124 describes a protective garment comprising at least onelayer of an activated woven carbon fabric and a highly absorbent rayonlayer as well as a ribbed fabric such as corduroy on the body side ofthe carbon fabric. The preferred embodiment of the invention requiresthree layers of activated charcoal fabric, for protection againstchemical agents; it is doubtful that even three layers would preventliquid agent from penetrating the composite.

GB-A-1360277 discloses a casualty bag comprising a non-woven materialtreated for liquid-repellency to which activated charcoal powder isbonded, i.e. a two-layer protection composite. It is suggested thatactivated charcoal cloth is suitable, but liquid strike-through couldnot then be avoided.

All the systems described above rely on some form of liquid-repellingbarrier to hold liquids away from the charcoal. The charcoal then servesto absorb vapours only. Another layer of material is also required toprotect the charcoal from water vapour and water, and to prevent sweatpoisoning.

GB-A-2137608 described activated charcoal which has been treated toprovide liquid-repellency.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a protectiveclothing system designed to have the following characteristics: (i) ahigh level of protection, (ii) low physiological load, (iii) resistanceto abrasion, (iv) flame-retardant protection, (v) long wear times, (vi)good aging characteristics, and (vii) launderability.

According to the present invention, a composite suitable for use as aprotective material comprises, in combination:

(1) an outer layer of an abrasion-resistant, flame-retardant,water-repellent material;

(2) an intermediate layer comprising activated charcoal cloth treated toprovide liquid-repellency; and

(3) an inner layer of an abrasion-resistant material.

Clothing using material of the invention offers a high level ofprotection, such that no conventional clothing need be worn underneath.The physiological load on the wearer is low.

DESCRIPTION OF THE INVENTION

A highly schematic cross-section of an embodiment of the invention isshown (not to scale) in the accompanying drawing, by way ofillustration. The drawing shows an outer layer 1, an intermediate layer2 and an inner layer 3, respectively of materials as described above.Arrow A indicates the direction of passage of perspiration from the bodyof the wearer to the atmosphere; arrow B indicates the (opposite)direction of passage of air filtered by the material.

The intermediate and inner layers (2 and 3) are usually laminatedtogether. The outer layer 1 may be laminated to the intermediate layer,but lamination together of all three layers may give the compositeunnecessarily high rigidity. It is therefore preferred that the outer orinner material (and usually the outer) is sewn to the remainder of thecomposite material, e.g. at the seams of a suit.

A composite material according to the invention may be made up into anarticle of protective clothing such as a casualty bag or protectivesuiting, industrial or agricultural, especially a CBW suit, one-piece ortwo-piece, and various components of complete body cover, e.g. hood andmitts. Velcro (Trade Mark) fastenings and zips may be provided, inconventional manner.

The material of the outer layer may be woven or non-woven, and willusually have a degree of oil-repellency. An example of a suitablematerial is a two-by-one twill fabric having a polyamide warp thread anda modified acrylic weft thread, e.g. at a make-up weight of 118 g/m².Other examples are woven or non-woven aramid fibre materials, e.g. assold as Nomex, (Trade Mark), another fire-resistant orchemical-resistant breathable fabric, or a water-resistant breathablefabric such as Gore-Tex (Trade Mark).

This outer material should preferably also be treated with a, say,silicone water-repellent and a fire-retardant additive. The material maybe infra-red reflective. It will usually be showerproof but is notnecessarily waterproof.

The intermediate layer serves to adsorb poisonous fumes, while allowingthe inward passage of air and the outward transmission of water vapour.This layer may comprise activated charcoal cloth which has been treatedas described in GB-A-2137608, the contents of which are incorporatedherein by way of reference. The active carbon layer may include a gaspermeable surface coating of particulate hydrophobic material whichrenders the active carbon waterproof. Modified PTFE, or a higher loadingof PTFE than is generally described in GB-A-2137608 may be used, toincrease liquid repellency, as desired.

Activated charcoal cloth (ACC) is an activated carbon adsorbentavailable in the form of a woven, non-woven or knitted cloth of 100%pure activated charcoal. Therefore, it can be utilised like a normaltextile and can be directly laminated to other textile materials.Further, as it does not comprise a "carrying" material which has beenbonded with activated charcoal it does not shed its charcoal in handlingand it does not harden or degrade once the bonding agent ages. Underhumid or wet conditions ACC is proven to significantly out-perform allother available forms of activated charcoal.

The inner layer acts as a lining material, providing the product withincreased tensile strength, abrasion resistance and comfort (if, as maybe the case, it is worn next to the skin). Its extensibility should notbe significantly greater than that of the intermediate layer, to presentthe latter breaking. This inner layer may be non-woven or woven. Thelamination of the inner and intermediate layers causes no decline inadsorptive performance or in storage life of the charcoal cloth.

The weight of the three-layer composite of the invention may be, forexample, no more than 500, 450, 400 or 375, e.g. about 350, g/m². It isbreathable, having an air permeability of at least 25, 30, 35 or, mostpreferably, 40, and up to 100, e.g. about 45-50, cm^(3/) cm^(2/) sec at10 mm w.g. It allows the outward passage of perspiration, expressed bywater vapour transmission values of preferably at least 1500, morepreferably at least 2500, and most preferably 3000 or above, for exampleup to 5000, e.g. 3500-4000, g/m² /24 h at 100% relative humiditydifferential, at 37° C. The composite yet offers good chemicalprotection, of at least 4, preferably at least 6, more preferably atleast 8, hours in the second of the mustard liquid tests given in theExamples (below). Protection may be effective after at least 30 days'continuous wear. Storage stability may be up to 25 years under normalconditions, in sealed packaging.

Protective material according to the invention can provide greaterprotection from a toxic environment than the second type of knownmaterial (involving fixed carbon particles) described above. Moreover,the use of ACC imposes a very low physiological load.

Once encapsulated in the recommended materials composite, charcoal clothis completely protected from abrasion. As it is a 100% pure activatedcarbon fabric, the carbon cannot detach as it has been proven to do withpowder-loaded foams or bonded carbon spheres.

ACC is a non-flammable material. Although all protective clothingsystems will have a flame-retardant outer material, the application ofheat or flame to ACC will not cause it to melt or soften. Foam-backedmaterials and the bonding agents used to attach carbon to carriermaterials could suffer adversely from the application of heat or flame.

All protective clothing systems should be constructed such that they canendure continuous wear for 30 days. ACC would not suffer any degradationof its adsorptive performance during this period even after totalimmersion in water. ACC in clothing systems can be laundered, providedthat detergents are not used.

As ACC contains no bonding agents, no aging occurs in its adsorptiveperformance or its woven structure when in sealed packages. Itsshelf-life is therefore infinite in these conditions, unlike all otherforms of pseudo-carbon materials.

The high breathability of the novel material has the important advantagethat it should allow protective suits to incorporate areas ofimpermeable materials to provide protection against sustained abrasionto vulnerable areas and increased protection against areas of maximumthreat, i.e. shoulders, knees, elbows and trouser seat, without greatlyincreasing the physiological load on the wearer.

The following Examples illustrate the invention. The "outer","intermediate" and "inner" materials are those defined by thisspecification.

EXAMPLE 1

Outer layer: to British Ministry of Defence Specification UK/SC/3988C,cloth, twill, modacrylic and nylon, olive drab or disruptivelypatterned, water-repellent and flame-retardant.

Intermediate layer: Activated Charcoal Cloth, grade FMl/250 availablefrom Charcoal Cloth Limited, fluorochemically-treated to impart oil andwater-repellency.

Inner layer: Laminated to the inner surface of the charcoal cloth, awoven Kevlar material (100% T-29 Kevlar 1.5 dpf, yarn 80/2 cc, plainweave 50×40 warp and fill, 7.5 kg/m²), bonded using heat-fusiblepolyamide dot coating.

    ______________________________________                                        Physical properties of the composite                                          ______________________________________                                        Mass per unit area                                                                              approx. 355 g/m.sup.2 (dry)                                 Breaking strength >190 N/cm                                                   Air permeability  approx. 44 cm.sup.3 /cm.sup.2 /sec at 10                                      mm w.g.                                                     Water Vapour Transmission                                                                       approx. 3600 g/m.sup.2 /24 hrs.                             (at 100% RH Differential,                                                     37° C.)                                                                ______________________________________                                    

The intermediate-inner layer laminate had, for the same four properties,values of 225, 150, 68 and more than 4000 g/m² /24 h.

EXAMPLE 2

Example 1 was repeated, but using as the outer layer olive-drab,water-repellent woven Nomex 456 fabric (comprising 95% coloured Nomex 15 dpt and 5% T-29 Kevlar 1.5 dpf, yarn 37/2 cc, plain weave 70x47warp-and-fill, 15.25 kg/m²). The composite weighed 360 g/m² (dry), theair permeability was 47 units; otherwise the properties weresubstantially the same as in Example 1.

TESTS

1 μg droplets of liquid mustard were placed on the outer surface of thesample under test. The sample sat on a piece of test paper which issensitive to mustard penetration, in vapour or liquid form, at levelsdown to below 1 μg per drop of applied liquid. Detection of penetrationis seen by a colour change on the indicator paper from red to blue. Forconvenience, the sample and test paper were placed on a glass plate, anda time lapse camera and clock were set up under the sample to record theappearance of colour changes with time, even whilst the sample isunattended, e.g. overnight.

Liquid mustard drops were applied in isolation (in which case eachdroplet was covered by a polythene cover to prevent evaporation awayfrom the immediate area of the droplet), or at coverages of up to 9drops per 9 cm² (in which case a 0.5 m/sec airflow was passed over thesample surfaces and the droplets were uncovered).

The products of Examples 1 and 2 achieved similar protection times inboth tests. No liquid or vapour penetration of the samples occurred evenafter 6 days.

The products of the Examples can satisfactorily be sewn together intoCBW protective clothing or other items, as described above.

I claim:
 1. A multi-ply material suitable for use as a protectivematerial, which comprises, in combination:(1) an outer layer of anabrasion-resistant, water-repellent material; (2) an intermediate layercomprising activated charcoal cloth treated to provideliquid-repellency; and (3) an inner layer of an abrasion-resistantmaterial, said intermediate layer being adhesively bonded to said innerlayer.
 2. A material according to claim 1, wherein the outer layer isnot laminated to the intermediate layer.
 3. A material according toclaim 1, which weighs no more than 500 g/m².
 4. A material according toclaim 1 which has an air permeability of at least 25 cm³ /cm² /sec at 10mm w.g.
 5. A material according to claim 1, which has a watertransmission value of at least 1500 g/m² /24 h at 100% RH at 37° C. 6.An article of protective clothing which comprises composite materialaccording to claim
 1. 7. An article according to claim 6, said articleof clothing including portions adapted to cover a joint or vulnerablepart of the wearer's adapted to cover a joint or vulnerable part of thewearer's anatomy, wherein said portions comprise impermeable material.8. A material according to claim 2, which weighs no more than 500 g/m².9. A material according to claim 2, which has an air permeability of atleast 25 cm³ /cm² /sec at 10 mm w.g.
 10. A material according to claim3, which has an air permeability of at least 25 cm³ /cm² /sec at 10 mmw.g.
 11. A material according to claim 2, which has a water transmissionvalue of at least 1500 g/m² /24 h at 100% RH at 37° C.
 12. A materialaccording to claim 3, which has a water transmission value of at least1500 g/m² /24 h at 100% RH at 37° C.
 13. A material according to claim4, which has a water transmission value of at least 1500 g/m² /24 h at100% RH at 37° C.
 14. An article of protective clothing which comprisescomposite material according to claim
 2. 15. An article of protectiveclothing which comprises composite material according to claim
 3. 16. Anarticle of protective clothing which comprises composite materialaccording to claim
 4. 17. An article of protective clothing whichcomprises composite material according to claim
 5. 18. A materialaccording to claim 1 which exhibits chemical protection such that liquidmustard drops applied in isolation will to penetrate the compositematerial over a period of at least four hours.
 19. A material accordingto claim 1 wherein the intermediate layer comprises an active carbonmaterial including a gas permeable surface coating of particulatehydrophobic material which renders the active carbon waterproof.
 20. Anarticle according to claim 6, wherein said layers are fastened togetherby stitching at seams of the article of clothing.
 21. A protective suitadapted to be worn by a person, said suit comprising a compositematerial that comprises, in combination:an outer layer of anabrasion-resistant, water repellent-material; an intermediate layercomprising activated charcoal cloth treated to provideliquid-repellency; and an inner layer of an abrasion-resistant material;said layers being held together by stitching at seams of the protectivesuit.